1. Field of the Invention
This invention generally relates to the field of nuclear medicine. In particular, it relates to the field of radiation diagnosis and to examinations of a patient by means of a scintillation camera. Still more particularly, this invention relates to a housing or container for carrying a radioactive isotope which housing is to be attached to the patient's body, the isotope thereby serving as a motion detector or as an anatomical marker for nuclear images.
2. Description of the Prior Art
In nuclear medicine, a radioactive tracer such as technicium is administered to a patient undergoing examination, and the distribution of the tracer in the patient's body is viewed by aid of a scintillation camera.
A problem associated with this kind of nuclear examination is the movement of the patient. When the patient moves during examination, a blurred image may result.
In order to overcome this disadvantage, a diagnostic motion correction scheme has been developed, see U.S. patent application Ser. No. 324,090, filed by Mark W. Groch and James T. Rhodes, under the title "Motion Correction Circuitry and Method for a Radiation Imaging Device", on Dec. 1, 1981. The disclosure of this application is incorporated herein by reference.
According to this motion correction scheme, a blurring of e.g. .sup.99m Tc gated blood pool images due to patient motion is corrected. This is accomplished by introducing a special radioactive point source, in particular a gamma ray emitting radioisotope, whose energy window lies outside that of .sup.99m Tc, into the field-of-view of the scintillation camera. The point source remains outside of the patient's body; thus, no gamma rays emitted from the source are scatter events. Then the centroid of the point source is monitored. When a change in the centroid of the point source is detected due to patient motion, the .sup.99m Tc events are corrected and repositioned to take into account the motion artifact. In cardiac studies, for instance, the movement of a special radioactive source which is fixed to the chest of the patient is detected. This movement is subtracted from the detected radiation coming from the tracer isotope of different energy signature flowing in the blood through the heart. Thus the "dual isotope motion correction scheme" eliminates the motion blur in the images as they are acquired.
There are two problems that one must keep in mind when using such a centroid (point) source external to the patient's body during image acquisition. First, the special radioactive point source must be within the field-of-view and the events emitted must be detected through the collimator of the camera. Second, since the point source should be encased in a shielding medium which will attenuate .sup.99m Tc events emanating from the patient's body, the point source must not obstruct any important anatomical structures in the field-of-view.